Application of nearly linear solvers to electric power system computation

To meet the future needs of the electric power system, improvements need to be made in the areas of power system algorithms, simulation, and modeling, specifically to achieve a time frame that is useful to industry. If power system time-domain simulations could run in real-time, then system operators would have situational awareness to implement and avoid cascading failures, significantly improving power system reliability. Several power system applications rely on the solution of a very large linear system. As the demands on power systems continue to grow, there is a greater computational complexity involved in solving these large linear systems within reasonable time. This project expands on the current work in fast linear solvers, developed for solving symmetric and diagonally dominant linear systems, in order to produce power system specific methods that can be solved in nearly-linear run times. The work explores a new theoretical method that is based on ideas in graph theory and combinatorics. The technique builds a chain of progressively smaller approximate systems with preconditioners based on the system\u27s low stretch spanning tree. The method is compared to traditional linear solvers and shown to reduce the time and iterations required for an accurate solution, especially as the system size increases. A simulation validation is performed, comparing the solution capabilities of the chain method to LU factorization, which is the standard linear solver for power flow. The chain method was successfully demonstrated to produce accurate solutions for power flow simulation on a number of IEEE test cases, and a discussion on how to further improve the method\u27s speed and accuracy is included --Abstract, page iv

Cellular Multilayer Perceptron for Prediction of Voltages in a Power System

With the increase in renewable energy sources connected to the power grid, better identification tools are needed for power system voltage profile prediction. Current deregulation trends have led to voltages operating close to stability limits which increases the need for quick estimation tools for system security and contingency analysis. This paper presents a Cellular Multilayer Perceptron (CMLP) architecture for fast identification and prediction of bus voltages. the CMLP method is compared with a standard MLP neural network for bus voltage prediction on the 12-bus three-area test power system. CMLPs can represent a direct mapping of any power system simplifying the equations and allowing for easy scalability to large power systems. © 2009 IEEE

Voltage Prediction using a Cellular Network

Better identification tools are needed for power system voltage profile prediction. the power systems of the future will see an increase in both renewable energy sources and load demand increasing the need for quick estimation of bus voltages and line power flows for system security and contingency analysis. a Cellular Simultaneous Recurrent Neural Network (CSRN) to identify and predict bus voltage dynamics is presented in this paper. the benefit of using a cellular structure over traditional neural network architectures is that the network can represent a direct mapping of any power system allowing for easier scalability to large power systems. a comparison with a standard single SRN is provided to show the advantages of this cellular method. Two types of disturbance are evaluated including perturbations on the power system generators and on the least stable loads. the method is also evaluated for a case involving a transmission line outage. ©2010 IEEE

Improving glycosylation profiles and cell culture performance with a sensitive cell line in commercial manufacturing

A history of sporadically poor culture performance in the inoculum train and subsequent production cultures has been observed in a CHO cell line expressing a recombinant mAb X, resulting in insufficient titer for forward processing downstream. Through data analysis and experimentation in controlled bioreactors, this poor performance has been linked to seed train culture conditions- primarily seed train culture pH. Standard manufacturing practices for pH monitoring and control were modified to more precisely control culture pH to desired set point. Non-standard metrics (such as cell size and oxygen uptake rate) have been used to monitor seed train cultures. Evidence of the poor growth phenotype can also be found in elevated levels of binding immunoglobin protein (BiP) in the seed train culture cells. With seed train pH control improvements and enhanced monitoring in place, the poor culture performance has not been observed in recent commercial campaigns. In addition to reduced titer, product quality is also impacted when slower growth is observed in production culture, specifically out of specification high afucosylated species is observed. For one case of poor production performance that resulted in a high out of specification result for the afucosylated species, a review of equipment, cell age, raw material, adventitious agent testing, mechanical and process change records, and production media composition did not identify anything that could be linked to the slow growth observed. However, trend analysis revealed an abnormally high ammonium level in the early inoculum train stage. This case showed that minor deviations in the inoculum train cultures could result in poor performance in production cultures later, ultimately resulting in product quality failures. In order to reduce impact to product quality using this sensitive cell line, efforts to move the process into a more robust zone have been explored. Modified pH control strategies and impact to culture performance and product quality control will be discussed

HEXACO personality predicts counterproductive work behavior and organizational citizenship behavior in low-stakes and job applicant contexts

This study examined the degree to which the predictive validity of personality declines in job applicant settings. Participants completed the 200-item HEXACO Personality Inventory-Revised, either as part of confidential research (347 non-applicants) or an actual job application (260 job applicants). Approximately 18-months later, participants completed a confidential survey measuring organizational citizenship behavior (OCB) and counterproductive work behavior (CWB). There was evidence for a small drop in predictive validity among job applicants, however honesty-humility, extraversion, agreeableness, and conscientiousness predicted lower levels of CWB and higher levels of OCB in both job applicants and non -applicants. The study also informs the use of the HEXACO model of personality in selection settings, reporting typical levels of applicant faking and facet-level predictive validity. (C) 2018 Elsevier Inc. All rights reserved

Swarm Intelligence and Evolutionary Approaches for Reactive Power and Voltage Control

This paper presents a comparison of swarm intelligence and evolutionary techniques based approaches for minimization of system losses and improvement of voltage profiles in a power network. Efficient distribution of reactive power in an electric network can be achieved by adjusting the excitation on generators, the on-load tap changer positions of transformers, and proper switching of discrete portions of inductors or capacitors. This is a mixed integer non-linear optimization problem where metaheuristics techniques have proven suitable for providing optimal solutions. Four algorithms explored in this paper include differential evolution (DE), particle swarm optimization (PSO), a hybrid combination of DE and PSO, and a mutated PSO (MPSO) algorithm. The effectiveness of these algorithms is evaluated based on their solution quality and convergence characteristic. Simulation studies on the Nigerian power system show that a PSO based solution is more effective than a DE approach in reducing real power losses while keeping the voltage profiles within acceptable limits. The results also show that MPSO allows for further reduction of the real power losses while maintaining a satisfactory voltage profile

Fishing For Food: Values and Benefits Associated With Coastal Infrastructure

While there is substantial literature about the socio-cultural characteristics and values associated with recreational and commercial fisheries in the U.S., studies directed at those who ‘fish for food’—those who depend on consuming their catch to various degrees—are relatively sparse. Using qualitative data collected through 80 semi-structured interviews with fishers in the summer and fall of 2018 in Carteret County, North Carolina, this study aims to better understand the group of recreational fishers who consume their catch by describing social and cultural dimensions and values associated with fishing for food, examining the role of infrastructure in facilitating access to benefits associated with this activity, and considering how knowledge of existing licensing regulations surrounding subsistence license waivers affect this fishing community. Interviews conducted at free public fishing structures in the region revealed that fishers derive a variety of values and benefits from fishing at these sites, including access to recreation, nutrition, a social community, and mental health benefits, which were found to be negatively impacted by Hurricane Florence in September 2018. We also found an informal economy of sharing catch on- and off-site that extends the reach and benefits facilitated by public infrastructure to people beyond those using it directly. Overall, we call for conceptualizations of ‘fishing for food’ that include aspects that go beyond traditional definitions of ‘subsistence’ or ‘recreational’ fishing such as food security, access, and less obvious social and cultural motivations behind the activity. These findings are a compelling rationalization for the creation and maintenance of formal and informal fishing places locally and, by extension, in other coastal areas, given the array of benefits provided by access to these types of locations

The Spectrum of Yang Mills on a Sphere

In this note, we determine the representation content of the free, large N, SU(N) Yang Mills theory on a sphere by decomposing its thermal partition function into characters of the irreducible representations of the conformal group SO(4,2). We also discuss the generalization of this procedure to finding the representation content of N=4 Super Yang Mills.Comment: 18 pages v2. references added. typos fixe

Applying phylogenomics to understand the emergence of Shiga Toxin producing Escherichia coli O157:H7 strains causing severe human disease in the United Kingdom

Shiga Toxin producing Escherichia coli (STEC) O157:H7 is a recently emerged zoonotic pathogen with considerable morbidity. Since the serotype emerged in the 1980s, research has focussed on unravelling the evolutionary events from the E. coli O55:H7 ancestor to the contemporaneous globally dispersed strains. In this study the genomes of over 1000 isolates from human clinical cases and cattle, spanning the history of STEC O157:H7 in the United Kingdom were sequenced. Phylogenetic analysis reveals the ancestry, key acquisition events and global context of the strains. Dated phylogenies estimate the time to the most recent common ancestor of the current circulating global clone to 175 years ago, followed by rapid diversification. We show the acquisition of specific virulence determinates occurred relatively recently and coincides with its recent detection in the human population. Using clinical outcome data from 493 cases of STEC O157:H7 we assess the relative risk of severe disease including HUS from each of the defined clades in the population and show the dramatic effect Shiga toxin complement has on virulence. We describe two strain replacement events that have occurred in the cattle population in the UK over the last 30 years; one resulting in a highly virulent strain that has accounted for the majority of clinical cases in the UK over the last decade. This work highlights the need to understand the selection pressures maintaining Shiga-toxin encoding bacteriophages in the ruminant reservoir and the study affirms the requirement for close surveillance of this pathogen in both ruminant and human populations